Cancel dropbox subscription

If you subscribed via an iTunes account you need to log into that account and you should get a 'cancel' option to stop it auto-renewing : View, change, or cancel your subscriptions - Apple Support

(Removing the credit card from an account won't stop an iTunes subscription, that would just mean that iTunes wouldn't be able to collect the money for it and the account therefore going into debt and not being able to download anything ; deleting an app also won't stop its subscription.)

Did Apple resolve this issue for you? And do you remember ordering Dropbox?

try again Apple

You already know that Apple are not here, and that these are user forums.

I assume that the subscription is being paid through that iTunes account, its subscription payments show on that account's purchase history ?

Yes sure....

Is funny the suggestion, are don't exist in the subscription page of ITunes the button to cancel, are exist for Netflix but not for Dropbox... try again Apple...

And in the payment history too...

That, based on google translate, seems to be giving you the option to resubscribe i.e. it's not currently set to auto-renew